1. Field of Invention
The present invention relates to a retainer for a roller bearing for holding a rolling member such as a ball, in which a flat portion is formed in a ball pocket having a spherical inner circumferential surface.
2. Description of the Related Art
A conventional retainer for a roller bearing (hereinafter simply referred to as a retainer) will now be described with reference to FIG. 5 which shows an example of a retainer 1 used in a bearing to which a load is applied in an axial direction, i.e., a radial roller bearing. The retainer 1 is formed of a ring-shaped member. A plurality (eight in the drawing) of ball pockets 2 for holding rolling members (not shown) such as balls are formed on one side surface in the axial direction. Inner circumferential surfaces (concave surfaces) of these ball pockets 2 are formed into a spherical shape corresponding to the shape of the outer circumferential surfaces of the rolling members. The rolling members are mounted on the retainer 1 to thereby form a bearing body for the roller bearing.
In the above-described prior art, in which the retainer holds the rolling members only with the single concave surface (spherical surface) formed in each ball pocket, in order to reduce vibration of the retainer, it is effective to reduce a curvature of the concave surface of the ball pocket and to narrowly hold the rolling member, i.e., to use a method to hold of holding the rolling member so as not to generate any gap between the rolling member and the concave surface. However, in the above-described case, lubricant is not introduced in the space between the rolling member and the concave surface. In fact, in some cases, the lubrication for the rolling member would be sacrificed. Thus, there is a fear that a service life of a normal noise preventing function would be shortened.
Also, inversely, it is possible to increase the curvature of the concave surface of the ball pocket in view of sufficient lubrication to the rolling members. However, in such a case, an amount of movement of the retainer relative to the rolling member is increased and vibration is generated in the retainer when the bearing is rotated producing the fear that the service life of the noise preventing function that should be maintained normally would be degraded.